Capturing movement of an articulated chain, such as a robot or a human, is a technique used in many applications, for example biomechanical analysis, remote manipulation, animation of virtual people, or man-machine interfaces by gesture in which the articulated chain is usually an upper limb comprising an arm, a forearm and a hand.
There are devices comprising two distinct portions, one placed on a moving object, the other fixed relative to the movement of the object. This type of device requires installing material both on the object and in the environment of the object, which causes problems if obstacles are present between these various materials, and limits the scope of such a device. The installation and calibration time is long and the cost is high.
There are also very widespread devices, based on optics, as described for example in documents US 2003/0215130 A1 and US 2005/00883333 A1, making it possible to reconstruct the movements of the body based on images seen by cameras placed all around the movement sequence of the body. Highly visible markers are placed on the moving object. A process carried out by a computer tool makes it possible to determine the position in three dimensions, or 3D, of each marker through the principle of stereoscopy. However, the problems of optical occlusion remain numerous which makes the minimum number of cameras used high.
Certain authors propose to reduce this type of drawback, as appears, for example, in the document “Skeleton-Based Motion Capture for Robust Reconstruction of Human Motion” (L. Herda; P. Fua; R. Plänkers; R. Boulic; D. Thalmann, Computer Graph lab (LIG), EPFL—web 01/2000). Other authors propose processing methods based on the silhouette extracted from a single camera by associating therewith a model of the moving object, for example in the document “Marker-free Kinematic Skeleton Estimation from Sequences of Volume Data” (C. Theobalt; E. Aguiar; M. Magnor; H. Theisel; H-P. Seidel; MPI Informatik).
However, even though these drawbacks are reduced, they remain.
The systems based on electromagnetism reconstruct the angles and the positions of the sensors placed on the object.
The ultrasound systems, like the optical systems, find the positions of the emitters. These two technologies suffer from the same limitation in space as the camera-based systems.
Other devices exist in a single block, placed on the moving object or body, such as exoskeletons, which use a reconstruction of the movement based on measurements of angles taken by angle sensors placed at the articulations. These devices make it possible to dispense with the spatial limitation of the movement capture. However, these devices are constricting because they comprise mechanical articulated arms and/or legs placed on the structure or the person, which are considerably weighty and awkward.
Other devices, for example described in document FR2897680, use inertio-magnetic sensors, such as gyrometers, accelerometers, or magnetometers, and use inter-segment angle calculations or solid elements of the articulated chain which make it possible to reconstruct the complete movement of the articulated chain. It is a device that is easy to produce.